As the result of the present invention, the following prior art approaches were uncovered:
______________________________________ Inventor Ser. No. Date ______________________________________ Avedik et al 4,138,658 Feb. 6, 1979 Joseph C. Gray 3,572,462 Mar. 30, 1971 L. R. Padberg, Jr. 3,514,749 May 26, 1970 S. Epstein et al 3,373,400 Mar. 12, 1968 A. J. Hintze 2,691,939 Oct. 19, 1954 ______________________________________
The 1968 patent to Epstein et al (U.S. Pat. No. 3,373,400) is an apparatus and process for determining certain geophysical properties, such as sound velocity, in the ocean bottom. In Epstein, a series of explosive charges are detonated in a predetermined order at spaced time intervals in order to permit discrete recordation of the bubble pulse characteristics of each detonation. One explosive charge occurs above the seafloor, a second explosive charge occurs on the seafloor, and a third explosive charge occurs under the seafloor. A hydrophone is utilized on the surface of the sea to receive the resulting explosive shock and wave forms. The Epstein approach utilizes an apparatus for embedding the third charge into the seafloor and is not adapted to be reused for different measurements being totally self destructive.
The 1971 patent issued to Gray (U.S. Pat. No. 3,572,462) sets forth an apparatus for use in seismic explorations wherein an artificial shock wave is created from an energy source on the seafloor being directed into the seafloor for reflection from a sub-surface formation. Receipt of the reflection from the sub-surface formation occurs in an energy receptor which is located separately and remote from the energy source. Such apparatus and method of Gray is not suitable for determining the geophysical properties of the layers of the sediment near the seafloor. The advantage of the Gray approach over other similar approaches lies in its ability to provide substantially vertical (or normal) reflection from the energy source through to the substrata and back into the receptor rather than using oblique reflection.
The 1954 patent issued to Hintze (U.S. Pat. No. 2,691,939) relates to an apparatus for planting an explosive charge below the seafloor. The 1979 patent issued to Avedik et al (U.S. Pat. No. 4,138,658) sets forth a seismograph for use on the seafloor. And, the 1970 patent issued to Padberg, Jr. (U.S. Pat. No. 3,514,749) relates to a method and apparatus for conducting seismic explorations from aircraft. The Padberg, Jr. apparatus has for its purpose to measure the existence of sub-surface discontinuities.
Only the Epstein approach is adopted for generating data concerning the geophysical properties of local regions of the seafloor. None of the other prior patented approaches provide such data.
As will be presented in the following, the seafloor velocity and amplitude measurement apparatus and method of the present invention generates data on the various layers in the near seafloor region of the sediments utilizing an approach different from Epstein (expansion of a gas bubble). And, one that generates an acoustic pulse in the sediments and analyzes the resulting pressure wave from the pulse at a point in the sediments vertically below the generation of the acoustic pulse. Epstein, to the contrary, receives his data at a point on the surface of the ocean generally obliquely located from the explosive sources. None of the prior art approaches discuss measurement of the amplitude of the received pressure wave.